Interesting, I didn't realize that Russia was already renting out the base pre-2014. Thank you for that context.

Perhaps an option could be that Ukraine gets their land back, but there's some agreement that Russia can rent out the land around the port at Sevastopol.

Ukraine gets paid for the use of their land (and ultimately they still own it), and Russia gets exclusive access to that part of the port where they can do whatever they need.